 #include <stdio.h>
 #include <specfunc/gsl_sf_bessel.h>
 
 int
 main (void)
 {
   double x = 5.0;
   double y = gsl_sf_bessel_J0 (x);
   printf ("J0(%g) = %.18e\n", x, y);
   return 0;
 }
